Electron velocity distribution function measurement in microwave cathode plume by incoherent laser Thomson scattering

In this work, we conducted an incoherent laser Thomson scattering (incoherent LTS) to measure the electron velocity distribution function at the plume region of a microwave cathode. The result obtained from incoherent LTS shows the electron density of 10^18 m^-3 and the electron temperature of 2-4 eV, which is validated by the comparison with a Langmuir probe measurement. Additionally, the incoherent LTS shows the EVDF is non-Maxwellian EVDF at a low propellant flow rate, whereas Maxwellian EVDF at a high propellant flow rate, indicating that the electron heating and cooling mechanism depends on the propellant flow rate.